The present invention relates to flame retardant polycarbonate-based thermoplastic resin composition with improved flame retardency, mechanical properties non-juicing property and good appearance, that is useful for the electric and electronic products housings. More particularly, the present invention relates to a polycarbonate-based thermoplastic resin composition which comprises a polycarbonate, a rubber modified styrene graft copolymer, a vinyl copolymer, phosphagen, phosphate compounds and a fluorinated polyolefin.
Polycarbonate molding compositions are widely used for the parts of electrical products and automotive components as having excellent transparency, high impact strength, and flame retardant properties. However, having poor processability during molding process, polycarbonate resins are usually used by blending with other kinds of resins. For example, molding compositions comprising a polycarbonate resin and a styrene-containing copolymer have good processability as well as high-notched impact strength.
Furthermore, the polycarbonate molding compositions used for parts of home appliances and computers should have particularly high flame resistance as well as the mechanical properties. For this purpose, halogen and/or antimony containing compounds have been used to render flame retardant property- to thermoplastic molding compositions. In U.S. Pat. Nos. 4,983,658 and 4,883,835, a halogen-containing compound is disclosed as a flame retardant. The halogen-containing compound, however, is fatally harmful due to the toxic gases generated during combustion, and therefore nowadays the halogen-free resin compositions are used widely.
As to a common composition without the halogen compound to render the flame resistance, it illustrates the composition using the phosphate typically. For example, U.S. Pat. No. 4,692,488 discloses fire retardant composition comprising a halogen-free aromatic polycarbonate resin, a halogen-free copolymer of styrene and acrylonitrile, a halogen-free phosphorus compound, tetrafluoroethylene polymers and a small amount of ABS graft polymer. The use of a phosphorus compound and perfluroalkane polymer to render flame retardency to a polycarbonate/ABS resin composition, as disclosed in U.S. Pat. No. 4,692,488, prevents the dripping of flaming particles during combustion. While these molding compositions indeed have adequate flame retardant behavior and mechanical properties, unsatisfactory surface crack due to the migration of flame retardant during a molding process, called xe2x80x9cjuicingxe2x80x9d, might occur.
U.S. Pat. No. 5,030,675 describes flame retardant, thermoplastic molding composition prepared from an aromatic polycarbonate, ABS polymer, polyalkylene terephthalate together with monophosphates and fluorinated polyolefins as flame retardants. Good stress cracking resistance is accompanied by deficiencies in notched impact strength, together with unsatisfactory heat resistance when exposed to elevated temperatures during processing.
Oligomeric phosphates are also known as flame retardants. Japanese Pat. Laid Open Publication 59-202,240 describes that such compounds can be used as flame retardants in polyamide or polycarbonate. However, this publication contains no indication of any improvement in stress cracking resistance by adding the oligomeric phosphate to polycarbonate molding compound.
U.S. Pat. No. 5,204,394 describes a polymer mixture comprising an aromatic polycarbonate, a copolymer and/or graft copolymer containing styrene, together with polyphosphates as flame retardants. Such a mixture has a poor compatibility between phosphate ester oligomer and polycarbonate, which leads to reduction of the weld-line strength.
U.S. Pat. No. 5,061,745 describes a polycarbonate molding compounds consisting of an aromatic polycarbonate, ABS graft copolymer, monophosphates as flame retardants. In processes using polyphosphates, the occurrence of juicing phenomenon occurs during molding process because the triarylphosphate form the laminate on the surface due to the volatility, and also the heat resistance of compound is lowered by thermal decomposition of oligomeric phosphate, which leads the injection molded articles to have black stripes on the surface.
U.S. Pat. No. 5,672,645 describes flame retardant polycarbonate/ABS molding composition containing an aromatic polycarbonate, a vinyl copolymer, a graft copolymer, a combination of a monophosphate ester and an oligomeric phosphate ester as flame retardants, and a fluorinated polyolefin. In this patent, resorcinol or hydroquinone derivatives were used as an oligomeric phosphate esters, but it is known that the compatibility of resorcinol or hydroquinone type oligomeric phosphorus flame retardant with polycarbonate resin is not so good that the impact strength of these composition can be lowered and surface crack due to the migration of flame retardant to the surface of molded parts still occurs. And also black stripes on the surface of molded parts occur by the thermal decomposition of these resorcinol or hydroquinone derived polyphosphate.
Japanese Pat. Laid Open Publication Hei-6-100785 discloses incorporation of silicone resin or phosphagen to the flame retardant resin composition consisting of thermoplastic resin and phosphorus type compound or red phosphorus to prevent dripping of flaming particles during combustion. However, this publication contains no indication of any improvement in flame retardency as well as weld-line strength and other property by adding phosphagen.
EP 728811 discloses flame retardant resin composition consisting of an aromatic polycarbonate, a vinyl copolymer, a graft copolymer, and an oligomeric phosphagen. This composition using oligomeric phosphagen as a flame retardant imparts non-dripping of flaming particles during combustion without any special anti-dripping agent, and also imparts the good heat resistance and impact strength. However, fluidity of the composition is lowered due to addition of oligomeric phosphagen, which leads to poor processability, and causes black stripes on the surface of injection molded articles. Furthermore, the weld-line strength of this composition is lowered, since compatibility of polycarbonate with oligomeric phosphagen is poor.
In view of the foregoing circumstances, the inventors of the present invention have formulated various thermoplastic resin compositions and carried out extensive studies on their heat resistance, flame retardency, impact strength, processability, and appearance, and found that a resin composition comprising polycarbonate resin, rubber modified styrene graft copolymer, vinyl copolymer, phosphagen compound, phosphate ester and fluorinated polyolefins has a well-balanced physical properties such as improved heat resistance, flame retardency, impact strength, heat resistance, processability, and good appearance, without causing the juicing phenomenon, leading to completion of the present invention.
An object of the invention is to provide a flame retardant thermoplastic resin composition with good combination of flame retardency, mechanical physical property strength including weld-line strength, good processability, stress crack resistance and heat resistance, which comprise a polycarbonate, a rubber modified styrene graft copolymer, vinyl copolymer, phosphagen compound, phosphate ester and fluorinated polyolefin.
Another object of the invention is to provide a flame retardant thermoplastic resin composition with the balanced properties such as impact strength, heat resistance, good processability, appearance, etc.
The present invention provides flame retardant thermoplastic molding composition comprises
(A) 45 to 99 parts by weight of a thermoplastic polycarbonate;
(B) 1 to 50 parts by weight of a graft polymer prepared by graft polymerizing
(B-1) 5 to 95 parts by weight of a mixture of
(B-1.1) 50 to 95 parts by weight of styrene, xcex1-methylstyrene, halogen or methyl ring-substituted styrene, C1-C8 alkyl methacrylates, C1-C8 alkyl acrylate or a mixture thereof and
(B-1.2) 5 to 50 parts by weight of acrylonitrile, methacrylonitrile, C1-C8 alkyl methacrylates, C1-C8 alkyl acrylate, maleic anhydride, Cl-C4 alkyl or phenyl N-substituted maleimides or a mixture thereof, onto
(B-2) 5 to 95 parts by weight of a polymer with a glass transition temperature of below xe2x80x9410xc2x0 C. and selected from a group consisting of butadiene rubbers, acryl rubbers, ethylene/propylene rubbers, styrene/butadiene rubbers, acrylonitrile/butadiene rubbers, isoprene rubbers, EPDM rubbers, polyorganosiloxane/polyalkyl(meth)acrylate rubber composite, and mixture thereof
(C) 0.5 to 50 parts by weight of a vinyl copolymer or mixture thereof prepared from
(C-1) 50 to 95 parts by weight of styrene, xcex1-methylstyrene, ring-substituted styrenes, C1-C8 alkyl methacrylates, C1-C8 alkyl acrylate or a mixture thereof and
(C-2) 50 to 5 parts by weight of acrylonitrile, methacrylonitrile, C1-C8 alkyl methacrylates, C1-C8 alkyl acrylates, maleic anhydride, phenyl N-substituted maleimides or a mixture thereof,
(D) 0.5 to 30 parts by weight of the mixture of the organic phosphorus compound based on 100 parts by weight (A)+(B)+(C) of (Dxe2x80x941) 5 to 95 parts by weight of linear phosphagen compound represented by the following formula (I-1) and/or cyclic phosphagen compound represented by the following formula (I-2) 
wherein, R represents alkyl, aryl, alkyl substituted aryl, alkoxy, aryloxy, amino or hydroxyl group, and n is 0 or an integer of 1 to 10. (D-2) 95 to 5 parts by weight of phosphate ester represented by the following formula (11) or the mixture thereof with 0.1 to 3 of M value 
wherein, R1, R2, R4, and R5 independently of one another are C6-C20 aryl or alkyl substituted C6-C20 aryl, R3 is alkylene, arylene, or arylene having alkyl group, M is 0 or 1 to 3.
(E) 0. 05 to 5 parts by weight, based on 100 parts by weight of (A)+(B)+(C), of fluorinated polyolefin resin with an average particle size of 0.05 to 1000 xcexcm and density of 2.0 to 2.3 g/cm3.